Which of the following statement(s) is/are false?
1. Pollen grains represents immatured male gametophyte.
2. In angiosperms partially developed male gametophytes are pollinated.
3. Generative cell is siponogenous while vegetative cell is spermatogenous.
4. Formation and differentiation of pollen grains is called microsporogenesis.
5. Pollen grains of some plants produce severe allergy and respiratory or bronchial diseases.
6. Pollen grains are poor in nutrients.
Which one of the following statements is correct?
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Solution
Cleistogamous flowers do not expose their reproductive parts. Anthers and stigma lie close to each other. Pure autogamy occurs since there is no chance of cross-pollination. Cleistogamy is the most efficient floral adaptation for promoting self-pollination. E.g., Viola mirabilis and Oxalis autosella.
The viability of seeds is tested by
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Solution
Dehydrogenase enzymes present in living tissue reduce the tetrazolium chloride to formazan, a reddish, water in soluble compound. This reaction occurs in or near living cells which are releasing hydrogen in respiration processes.Viable tissues produce a normal red-colour, weak living tissue produce an abnormal colour. Dead tissues do not stain, remaining usually white.
Which one of the following statements is correct?
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Solution
Sporogenous tissue is always diploid, endothecium is second layer of anther wall and perform the function of protection and help in dehiscence of anther to release the pollen. Hard outer layer of pollen is called exine but tapetum always nourishes the developing pollen.Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus (polypoid).
Product of sexual reproduction generally generates :
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Solution
Sexual reproduction leads to formation of new combination and appearance of variations. Genetic recombination,interaction etc.during sexual reproduction provides vigour and vitality to the offsprings. They better adapt themselves to changing environmental conditions and also plays an important role in evolution.
Advantage of cleistogamy is :
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Solution
Cleistogamy favours no dependence on pollinator because flowers never open. In such flowers, the anthers and stigma lie close to each other. When anthers dehisce in flower buds pollen grains come in contact with the stigma to effect pollination.
Seed coat is not thin, membranous in :
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Solution
The seed coat develops from integuments originally surrounding the ovule. It is thick and hard in coconut which protect the embryo from mechanical injury and from drying out.
Megasporangium is equivalent to :
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Solution
Ovule is also called integumented megasporangium. It develops into seed after fertilisation in spermatophytes. It occurs singly or in a cluster inside ovary with parenchymatous cushions called placenta.
Perisperm differs from endosperm in
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Solution
Perisperm is remnants of nucellus which is diploid(2n) but endosperm is triploid (3n). Perisperm occurs in the seeds of Black pepper, coffee, castor, cardamum, Nymphaea. Endosperm is the food laden tissue which is meant for nourishing the embryo in seed plants. In angiosperms the endosperm is formed as a result of vegetative fertilization, triple fusion or fusion of a male gamete with diploid secondary nucleus of the central cell.
Unisexuality of flowers prevents
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Solution
Unisexuality of flowers prevents. autogamy,but not geitonogamy. In self fertilisation, the male and female gametes are derived from the same individual.
Among plants,self fertilization also called autogamy is common in many cultivated species, eg., wheat and oats. However,self fertilization is a form of inbreeding and does not allow for the mixing of genetic material; if it occurs over a number of generations it will result in offspring being less vigorous and productive than those resulting from cross fertilization.